1. Field of the Invention
Embodiments of the present inventive concept relate to a multi-pass type image forming apparatus having an assembly to transmit power to an image-carrier and a developing unit through a coupling.
2. Description of the Related Art
Generally, image forming apparatuses are devised to form an image on a printing medium according to input signals. Examples of image forming apparatuses include printers, copiers, fax machines, and devices combining functions thereof.
One type of image forming apparatus is an electro-photographic image forming apparatus that includes an image-carrier, a light scanning unit, and a developing unit. The light scanning unit forms an electrostatic latent image on a surface of the image-carrier by irradiating light to the image-carrier that has been charged with a predetermined electric potential. The developing unit forms a visible image by supplying developer to the image-carrier on which the electrostatic latent image has been formed.
Commonly, yellow, magenta, cyan and black toners are used in the image forming apparatus, and thus four developing units may be necessary to attach the four colors of toners to the electrostatic latent image.
Image forming methods include a single-pass method in which each of four developing units includes an image-carrier, and a multi-pass method in which four developing units share a single image-carrier.
In the case of the multi-pass method, the four developing units are concentrically arranged about the image-carrier to share a single image-carrier.
A conventional multi-pass type image forming apparatus includes driving couplers to drive an image-carrier and four developing units, which are movable independently of one another and are adapted to be coupled to or separated from the image-carrier and the developing units.
The above-described configuration, however, may require devices to couple or separate the driving couplers to or from the image-carrier and developing units equal in number to the number of driving couplers. Therefore, the number of constituent elements is increased, causing higher manufacturing costs. Moreover, an expanded installation space may prevent reduction in the size of the image forming apparatus.